I've been studying new ideas for months now. The Swiss or Italian originally uses a boiled sugar water mixture which is drizzled over egg whites (much like divinity). It has a beautiful look when piped but sounds much harder. They end up doing all that beating then adding soft butter.
Mine is just tried and true since my mom got it from a club friend in the 50's. If you do try it, egg whites at room temp at the bottom, then the sugar, then the marshmallows, then the hot water (so the hot water doesn't touch part of the egg whites and cook them (never happened).
I did double it in a bowl for a two layer Strawberry marble cake I made up with a French Vanilla cake mix. I decorated it with halves of the new Whoppers strawberry malt balls. I tinted the frosting a pretty pink. But I wouldn't have gotten good coverage in the amounts I gave you so doubled it.
The only downside of both is that neither recipe cooks hot enough to pasteurize the egg whites. I still eat mine and family does but I've gotten a little hesitant to take it anywhere because salmonella has been blamed on eggs so much lately. And I don't think you can buy egg whites pastuerized in a carton at the store.
I know. I bought some Wilton Meringue Powder. I used it instead of egg whites in my recipe and it was awful. It might be ok in Wilton's frosting recipes as a stabilizer but not as say meringue shells or topping. It is pasteurized which is why I bought it.
Now the Italian Swiss hot syrup method would be hot enough long enough to pasteurize the raw beaten egg whites so it's something to think about. I found the best recipe I'd saved:
How to make Italian meringue buttercream
Pretty aren't they? Maybe worth learning but oh so careful with that hot syrup!